Epidural anesthesia is a popular method of treating acute and chronic pain. Most commonly, the “loss of resistance” (LOR) technique has been used to detect needle penetration into the space. This technique involves connecting the needle, such as a Tuohy needle, via a needle hub to a syringe filled with saline solution and continuously pushing on the piston of the syringe while the needle is inserted toward the epidural space until a loss of resistance is encountered indicating that the needle tip has entered the space. An alternative method of detection is the “hanging drop” (HD) technique which relies on visualizing the aspiration of a small volume of fluid from the hub of the needle as the pressure at the needle tip decreases below atmospheric level upon entry into the epidural space. However, conventional application of the hanging drop technique is less than optimal due to the number of manipulations required while the needle is inserted in a patient.
What is needed and provided by the present invention are new and improved apparatuses and methods for detecting needle penetration into a negative pressure (subatmospheric) space such as the epidural space.